A conventional hardware part of a computer is generally based on three kinds of common technologies: silicon for forming a transistor for logical operation, a memory and a signal amplifier; composite materials for isolating discrete component integrations; and copper for data transmission. Emergence of multi-core processors, concurrent and simultaneous execution of instructions, and development of software optimization improve a computer performance, while bringing higher requirement for computer hardware.
There is no more effective alternative for silicon based Complementary Metal-Oxide-Semiconductor (CMOS) transistor manufacturing process. Also, research and development for composite materials grows slowly. The data transmission becomes a main factor to limit the computer performance. For on-chip and on-board high-speed data transmission, when a signal rate is close to 10×109 bits/s, inherent characteristics of transmission lines such as skin effect and self-induction effect are becoming significant. It is difficult to distinguish between transmitted bits, probability of correct decoding is reduced, and signal integrity deteriorates seriously. When being transmitted on a transmission line, square wave may become wider and weaker. Sometimes, dispersion effect of a substrate should be stronger than that of copper transmission line, thereby further limiting the system performance. These factors reduce transmission distance of copper wire. In general, these problems may be addressed with pre-distortion, an active amplitude equalizer and a clock recovery, etc. However, circuit modules for the clock recovery, the active equalizer and preprocessor will increase corresponding power consumptions. In addition, in order to obtain higher throughput, it is not feasible to only increase a diameter of the copper bus. This is because the increased diameter of the bus and the reduced number of channels may cause the power consumption be increased, as well as the number of input/output ports requiring for grounding be increased.
Optical bus is a potential alternative for copper bus. In a multimode optical fiber or a polymer waveguide that has no bad attenuation or distortion on a signal of a band, a transmission distance of the signal can reach a few centimeters or even a few meters. However, transmission of a single bit in optical bus consumes more energy. While a new laser source can be directly modulated to 30×109 b/s and have sufficient reliability, it is expensive and may bring uncertainty. Among things, there is no reliable and economic integration process in mass production for the optical bus.
An article by Satoshi Fukuda, et al. entitled “A 12.5+12.5 Gb/s Full-Duplex Plastic Waveguide Interconnect” (ISSCC2011) introduces a millimeter-wave waveguide communication system. FIG. 1 shows a structural schematic diagram of a transmission waveguide in the existing millimeter-wave waveguide communication system. As shown in FIG. 1, the transmission waveguide employs plastic material with a dielectric constant of Er=2.6. Each plastic waveguide has a width of 8 mm and a thickness of 1.1 mm. An offset at a signal feed is 2 mm. Most of millimeter-waves transmitted through the plastic waveguide are confined within the plastic waveguide. Moreover, the above scheme employs the commonly configured circuit modules as RF transmitter/receiver, and uses an injection-locking approach instead of a phase-locked loop of high energy consumption to generate a synchronization carrier.
However, there are technical drawbacks in the above millimeter-wave communication system. Firstly, there is millimeter-wave leakage on an outer surface of the plastic waveguide, thereby resulting in a leaked electric field around the plastic waveguide, which extends about one wavelength. In order to reduce coupling of the leaked electric field, there must be enough distance between waveguides, which indirectly increases size of the waveguides and reduces the number of the waveguides. Secondly, there is millimeter-wave reflection on both ends of the waveguide, which leads to a decline in quality of a signal transmitted. Thirdly, the plastic waveguide has a low refractive index, which leads to an increased characteristic size of a signal channel, an increased size of the waveguide, and the reduced number of waveguides within a limited range. Next, a mixer and a voltage-controller oscillator for generating a millimeter-wave carrier are formed with circuits, so that the power consumption and noise of the whole millimeter-wave communication system are increased, especially a phase noise of a demodulation circuit is increased, thereby leading to an increased bit error rate and indirectly affecting a modulation rate of the signal transmitted. All of the above four technical drawbacks may affect data bandwidth, reduce the overall data throughput, and can't be adapted to a system such as a high performance computer.